1. Field of the Invention
This invention relates to improvements in high security post locks, and particularly to such devices which, for example, are adapted to pass through a movable door and its associated door frame.
2. Background Art
Medeco Security Locks, Inc., the assignee of the present invention, is well known for its high security locking devices. Medeco.RTM. locks are famous for their resistance to picking and drilling by virtue of their advanced twisting offset tumbler mechanical design and use of hardened steel components.
High security post locks, e.g. those for rolling or retractable garage doors and store fronts, have posed special problems. In general, it is desired to prevent movement of the rolling door relative to the frame by securing the door and frame together. While locks including a shaft terminating in a cam or other style protrusion are known, their designs have not rendered them truly suitable for the highest security applications. For example, many such designs cannot provide two-way security; i.e., both sides of the door cannot be secured against opening with a single lock.
U.S. Pat. No. 4,688,405 to Epstein, Aug. 25, 1978, illustrates a "concealed post lock" adapted to pass through a rolling door in order to secure the door to the door frame. The post lock includes a shaft passing through the door frame and the door, with an eccentric locking member rotatably mounted at the free end of the shaft. The locking member prevents the lock from being withdrawn from the door and frame.
The design of the Epstein post lock presents several disadvantages, however. The rotation of the eccentric relative to the post is limited by a shoulder projecting from the end of the post. The shoulder engages a corresponding flange on the eccentric, and the mating surfaces therebetween are exposed to the external environment. Debris collecting between the mating surfaces can be a source of friction and inhibit free operation of the lock, and could jam the lock and prevent its extraction. The lock cylinder and the shank of the eccentric are disposed in offset bores in the post, and are joined by a single locking pin. This arrangement introduces an inherent weakness into the device as well as manufacturing and assembly complexities with associated expenses.
U.S. Pat. No. 2,677,261 to Jacobi, May 4, 1954, relates to a door handle lock having a reduced diameter stem which passes through the door handle and into the door frame. A shaft passing through the stem terminates in a hook portion for preventing withdrawal of the lock.
U.S. Pat. No. 3,423,971 to Brunelli, Jan. 28, 1969, illustrates an automobile wheel lock. A locking rotatable cam element secures the lock over one of the lug nuts to prevent removal of the wheel.
A continuing need exists for a high security post lock of the type used for securing rolling or retractable-type doors. For highest security applications, the locking device should secure the door against opening from both sides and should be highly resistant to picking, drilling and other forms of tampering.